Machine tools of the above kind are universally well-known and are useful. They can be, for example, a double column planar-type milling machine, wherein the crossrail is held by two columns or stands on both sides of the machine table. It can just as well be a milling or drilling machine with only one column, on which a crossrail, designed as an outrigger, is held.
In machine tools of the above kind the column has vertical guides on which the crossrail can be moved vertically. Thus, by moving the crossrail vertically the tool unit can be moved a small distance above the workpiece, so that, when machining the workpiece, the tool does not have to carry out any undesired large vertical lifting movements relative to the tool unit.
The drawback with the machine tools of the aforementioned kind of construction is that the vertical guides of the column or columns are relatively quite complicated and they introduce the risk of chatter, if during a machining operation the crossrail not reliably clamped on the vertical guides.